ML20058K565
| ML20058K565 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 04/26/1974 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9102120490 | |
| Download: ML20058K565 (2) | |
Text
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hegulatory Docket File NSP NORTHERN STATES POWER COMPANY M IN N E A Pou s, MIN N E BOTA 55409 D
C April 26, 1974 O
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Dear Mr. Ziemann:
MONTICELID NUCLEAR GENERATING PIANT Docket No. 50-263 License No. DPR-22 Preliminary Response to April 4,1974 Letter on Prompt Relief Trip System We have discussed our proposed Prompt Relief Trip (PRT) System in the January 23, 1974 submittal entitled, " Permanent Plant Changes to Accom:nodate Equilibrium Core Scram Reactivity Insertion Characteristics" with supplements identified at the end of this letter. We have also had the opportunity to discuss the PRT system with you on February 20 and 21 and March 22, 1974.
Your April 4,1974 letter, concludes that insertion of PRT can not be approved unless the concern of inadvertent actuation of more than one safety / relief valve is satisfactorily resolved. Our January 23, 1974 submittal and supplements also discuss the removal of safety valves and installation of safety / relief valves piped to discharge into the torus suppression chamber. A March 14, 1974 letter from Mr. D J Skovholt, concludes that we can proceed with this portion of the modification.
To avoid doing work which could potentially require further changes later or extend our current refueling outage while awaiting your approval, we have proceeded with only the approved portions of the plant modification. We will not have the PRT system installed for our return to power. Through this letter, we wish to inform you of the status of plant changes which will be completed prior to our return to power and seek your concurrence that no significant safety considerations are involved. At a later date, we will respond to each of the areas identified in your April 4,1974 letter where additional information is required. Our April 10, 1974 letter shows that while these matters are being resolved, we can safely operate throughout Cycle 3 without the installation o f PRT.
9102120490 740426 CF ADOCK 050 63 m;
t NOR e HERN CTATEC POWER ContPANY
- - Mr. Dennis L Ziemann April 26, 1974 Page 2 Prior to returning to power, we will have removed the four safety valves which discharge directly to the drywell and will have installed four safety /
relief valves of greater flow capacitywhich discharge to the torus. Dual solenoid operators have been provided on each safety / relief valve with all associated wire routing in the drywell installed.
The new safety / relief valves will have the same controls and instrumentation as the existing valves. This includes controls for manual operation and monitoring of bellows leakage. Until we achieve further resolution of the PRT system design, the PRT cabinet will simply be used as a relay rack.
The only terminations made in the cabinet will be wiring connections associated with the manual control switch and bellows leakage monitoring circuitry, as designed, for the four new safety / relief valves; the viring and termination layout for these functions is essentially the same as that presently existing in the ADS cabinet for the original safety / relief valves. No PRT logic input or output cables will be installed and no PRT logic terminations will be made.
This installation of controls and instrumentation for the new safety / relief valves and the partial installation of PRT has been reviewed and evaluated by NSP and involves no significant safety considerations. We await your concurrence to permit our scheduled return to power.
Yours very truly, LC).
L 0 Mayer, PE Director of Nuclear Support Services i
LOM/MHV/1h cc: J G Keppler G Charnoff Minnesota Pollution Control Agency Attn. E A Pryzina Identification of NSP submittals to AEC-DL concerning, " Permanent Plant Changes to Accommodate Equilibrium Core Scram Reactivity Insertion Characteristics."
January 23, 1974 Original report March 8, 1974 Supplement No. I to January 23, 1974 report March 19, 1974 Errata for January 23, 1974 report April 20, 1974 Supplement (No. 2) to January 23, 1974 report April 26, 1974 Supplement No. 3 to January 23, 1974 report l
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